U3V70F9 how to protect against LC voltage spikes?

Support Voltage regulators
1

Hi,

I have 2 questions about the 9V Step-Up Voltage Regulator U3V70F9:

  1. There is no mention on the product page (https://www.pololu.com/product/2894) about how to protect against LC voltage spikes? On some other voltage regulator product pages, for example, the Pololu 9V Step-Up Voltage Regulator U3V12F9 (https://www.pololu.com/product/2116), i’ve seen the decoupling capacitor values are mentioned, but not for this product? Why? Does the U3V70F9 not require a decoupling capacitor?

  2. Also, why choose the 9V Step-Up Voltage Regulator U3V70F9 over the 9V Step-Up Voltage Regulator U3V12F9? In what applications would one be preferred over the other?

Thanks in advance for the help.

2

Hello,

We do not expect LC spikes to damage the U3V70F9 regulator, but if your input voltage spikes above 9V the spike will also be seen on the output. If that is a concern, you could add some capacitance across VIN and GND to help protect devices connected to the regulator’s output.

The U3V70F9 regulator can source a lot more current than the U3V12F9, so for higher current applications it is clearly a better choice.

-Derrill

3

Thank you for the response. I am using an 8.4 V DC battery as input to the U3V70F9 regulator. To protect against LC voltage spikes, what decoupling capacitor ratings do you suggest/recommend? I think a 35 V capacitor should be safe but what about its capacitance value?

4

To be really safe, I suggest doubling your 8.4V, so a 16-25V 33 μF or larger electrolytic capacitor should be fine (35V should be fine too).

-Derrill